It is possible to use a lambda probe in order to assess the combustion in an internal combustion engine with respect to a composition of a fuel-air mixture. The lambda probe includes a Nernst cell for determining a difference in the concentration of oxygen between two different gases, namely, the exhaust gas and usually an ambient air. A broadband lambda probe includes a cavity, a pump diaphragm and a measuring diaphragm. The pump diaphragm is controlled so as to convey exhaust gas through a fluid connection into the cavity or out of the cavity so that the tension on the measuring diaphragm, which practically represents a Nernst cell, has a predetermined value. It is then possible to determine the concentration of oxygen in the exhaust gas on the basis of the pump current. In another specific embodiment, it is possible to determine indirectly a concentration of nitrogen oxides in the exhaust gas in that the nitrogen oxides from the exhaust gas are catalytically split and the oxygen arising in the process is determined using another measuring diaphragm.
In order to establish a predetermined correlation between the pump current and a concentration of oxygen in the exhaust gas, normally each individually produced sensor must be adjusted individually. In one specific embodiment, the sensor is disposed on a ceramics substrate, it being possible to produce cuts in the surface of the ceramics using laser light in order to shorten the fluid connection and thus to reduce a flow resistance.